Nail-related wisdom sought

[undyingking]

Preparatory to moving we need to replace some skirting-board in the living-room. I've pulled the old board off, but the nails which were holding it are still embedded firmly in the wall and I can't work out how to get them out without pulling out large chunks of wall. But they're too flush for me to get a hacksaw in and cut them off. Or should I just make hollows in the back of the new board (which I'm going to be gluing on) to accommodate their heads? They're big old rectangular-cross-section things and look like they've been there for some time...